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Suspension: Setup and Technical Talk

Setting sag simply means getting the axles spot-on centered in the total up-down range of suspension movement with operational load.

Not all bikes are same. One has to measure the full range to be precise. Very difficult. Full extension is easy. Full compression is not. Published guidelines refer to fully unloaded extension and the loaded sag number will be a design calculated half way to full compression dimension. IOW the center of travel range. I have a winch in ceiling of shop for this purpose. Lift end of bike, measure full extension. Starting number.

Use preload adjusters to get to the loaded sag target number. If the preload adjuster needs to move way to edge of its travel then the spring is wrong size for rider/load. The spring will be tightening up too mich in one direction and loosening up too much in the other direction. Normal shocks can’t cope. An expensive suspension with compression rebound adjustment can band-aid a wrong spring. Partially.
 
EGR said:
Setting sag simply means getting the axles spot-on centered in the total up-down range of suspension movement with operational load.

Not all bikes are same. One has to measure the full range to be precise. Very difficult. Full extension is easy. Full compression is not. Published guidelines refer to fully unloaded extension and the loaded sag number will be a design calculated half way to full compression dimension. IOW the center of travel range. I have a winch in ceiling of shop for this purpose. Lift end of bike, measure full extension. Starting number.

Use preload adjusters to get to the loaded sag target number. If the preload adjuster needs to move way to edge of its travel then the spring is wrong size for rider/load. The spring will be tightening up too mich in one direction and loosening up too much in the other direction. Normal shocks can’t cope. An expensive suspension with compression rebound adjustment can band-aid a wrong spring. Partially.
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So if I read this right, the manual says I need a static sag of 1.44 inches so my total spring travel is 2.88 inches?
 
EGR said:
Nomenclature varies. 1.44 strikes me as not much. Maybe look up total suspension travel for your bike. Both ends. Numbers you measure should make sense with regard to those.

The loaded sag is what matters. Rider, gear on, and stuff sitting in saddle. Really helps to have a helper measure while you are balancing. There are gadgets available to help do it solo.

There is often a number published for simply the bike’s weight. IMO not useful much.
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I believe it is a Husky dirtbike. About 12” or travel. I think he will want about 4” of race sag and 1“ of static sag. The manual will say for sure.
 
Wow. Just had a quick look at internet wisdom. I’m dinosaur days conservative.

Stickin’ with loaded rolling out to begin set up session I want both axles in center of their up and down range. Feet, hands, butt and inner ears are valid measurement tools. Millimeters and click counts will follow.
 
Here's a couple pics from my manual. It's a 22-te300i.
20220406_181856.jpg
20220406_181847.jpg


Ant to be honest I didn't check static sag with the stock spring, just rider sag. I had it set to the manual and at 6mm not the 10mm the manual called for. With the lighter spring both static and rider was very close but the preload was about twice the recommended amount.
 
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Don't worry. I'm new to this 2t world now. Lots of learning for me. Next I think will be the power valve. Lol
 
SnakeOiler said:
Here's a couple pics from my manual. It's a 22-te300i.
20220406_181856.jpg
20220406_181847.jpg


Ant to be honest I didn't check static sag with the stock spring, just rider sag. I had it set to the manual and at 6mm not the 10mm the manual called for. With the lighter spring both static and rider was very close but the preload was about twice the recommended amount.
Click to expand...
Excellent. You have to squeeze the lighter a bit harder to get target sag. Total sense. Both springs can do your target. Overlap zone. I’d ride the lighter spring looking for bottom. If it does not bottom that would be my keeper because that’s my preference.

IMO the book numbers are for a starting zone.
 
EGR said:
Excellent. You have to squeeze the lighter a bit harder to get target sag. Total sense. Both springs can do your target. Overlap zone. I’d ride the lighter spring looking for bottom. If it does not bottom that would be my keeper because that’s my preference.

IMO the book numbers are for a starting zone.
Click to expand...

This is my line of thinking, with the heavier spring (stock) I'll have better feel though out more of the stroke of the shock. Plus less bottoming. I know that it worked pretty well in the desert at higher speeds. But I'm hoping to be in the mountains of Idaho this summer. So more technical slower trails are more likely. That's why I wanted to try and soften it up some. Hopefully with playing around with compression and rebound I'll be able to get at least close to my likely.
 
SnakeOiler said:
Ant to be honest I didn't check static sag with the stock spring, just rider sag. I had it set to the manual and at 6mm not the 10mm the manual called for. With the lighter spring both static and rider was very close but the preload was about twice the recommended amount.
Click to expand...
Maybe something is lost in the translation but these preload numbers seem excess. In my experience a one rate lower spring might need 3–4 mm more preload to achieve the desired sag.
 
SnakeOiler said:
This is my line of thinking, with the heavier spring (stock) I'll have better feel though out more of the stroke of the shock. Plus less bottoming. I know that it worked pretty well in the desert at higher speeds. But I'm hoping to be in the mountains of Idaho this summer. So more technical slower trails are more likely. That's why I wanted to try and soften it up some. Hopefully with playing around with compression and rebound I'll be able to get at least close to my likely.
Click to expand...
In slower technical riding on a WP Xplor shock I'd start from 120 mm sag and HSC open 2,5. Opening up the high speed compression makes it feel much softer.
 
From what I've read and understood, on "long" suspension travel/dirbikish stuff, race sag should be around 1/3 of suspension travel. That makes sense as big compression hits are expected.
I've also been explained that when one has to choose between a bit too much and not enough spring rate, one should select the stiff option. Something like it's better to waste a bit of travel than bottoming too often but that's my guess.
 
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Oldbear said:
Maybe something is lost in the translation but these preload numbers seem excess. In my experience a one rate lower spring might need 3–4 mm more preload to achieve the desired sag.
Click to expand...

I'm hoping to get the shock off today, and get a better measure on it. But I set the preload at assembly to the manual then installed the shock. To get the static sag I ended up making 2.5 revolutions on the adjuster. From what I can tell each revolution is about 3mm. So it seems that should over 7mm more than the manual.

The other thing that seems wrong is the stock spring is a 42 and the next one down I could find was a 39. That's a larger step down than most which are usually only 2 difference. But again I'm new too this stock working, I've more experienced with forks.
 
SnakeOiler said:
I'm hoping to get the shock off today, and get a better measure on it. But I set the preload at assembly to the manual then installed the shock. To get the static sag I ended up making 2.5 revolutions on the adjuster. From what I can tell each revolution is about 3mm. So it seems that should over 7mm more than the manual.

The other thing that seems wrong is the stock spring is a 42 and the next one down I could find was a 39. That's a larger step down than most which are usually only 2 difference. But again I'm new too this stock working, I've more experienced with forks.
Click to expand...
Ah, OK. The thread pitch is much less, IIRC on WP shocks it's from 1.0 to 1.5 mm, depending on the shock body.

3N step is really common in shock springs.

Here's a measured real-life example of my rear PDS shock.

75N spring
Preload 8 mm
Sag 37/110 mm

72N spring
Preload 10 mm
Sag 40/118
 
Oldbear said:
Ah, OK. The thread pitch is much less, IIRC on WP shocks it's from 1.0 to 1.5 mm, depending on the shock body.

3N step is really common in shock springs.

Here's a measured real-life example of my rear PDS shock.

75N spring
Preload 8 mm
Sag 37/110 mm

72N spring
Preload 10 mm
Sag 40/118
Click to expand...

I'm heading out shortly to take the shock off. I'll get better dimensions. The thread pitch looks finer, I was surprised myself. Unless I measured wrong.

I've been having a bad go of things lately. Everything is adding up to a boil over for me. Lol. I guess I need more seat time to free up head space.
 
Nener said:
That sounds like a lot, are we talking 3mm on the shock travel (=preload when expressed as mm) or wheel travel (sag) ?
Click to expand...
3mm is per revolution of the preload nut on the shock.
 
I got the shock off, doesn't make much sense to me. But the spring is around 5mm shorter than before. Would that be normal? I've never changed out springs with a new one. Anyhow I reset the preload to the manual (.470) plus another .187. That should get me close to my sag.
 
SnakeOiler said:
I got the shock off, doesn't make much sense to me. But the spring is around 5mm shorter than before. Would that be normal? I've never changed out springs with a new one. Anyhow I reset the preload to the manual (.470) plus another .187. That should get me close to my sag.
Click to expand...

I think you are putting too much faith in measurement based off of the shock. Sag measurements are the way to go. The only reason the spring measurements matter is to avoid coil bind and from the sounds of it, you are nowhere close to that.
 
All back together rider sag is a tad heavy, but it's easier to take preload off than put on while the shock is on the bike
 
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